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Trp Operon Mutations?

  1. Mar 25, 2015 #1
    1. The problem statement, all variables and given/known data
    "Based on your understanding of gene regulation in the cell and the function of the trp operon, describe how this process would be affected if there was a mutation in the operator region so that the operator could not carry out its function."

    also, just another question. What would occur if the trp repressor altered shape?

    2. Relevant equations

    3. The attempt at a solution
    I believe if a mutation occurred in that region, ultimately to the point where the operator could not carry out its task anymore the cell would no longer be able to metabolize Tryptophan . My question lies here, once the cell lacks the tools to metabolize Tryptophan what would occur?

    In regards to the shapeshifting, I believe that it would not longer be able to carry out its task which would ultimately call for the cell to continously produce Tryptophan on its own. However, what could result from this? I know that the presence of Tryptophan activates the repressor, but what would occur if the cell continuously made Tryptophan on its own?

    Last edited: Mar 25, 2015
  2. jcsd
  3. Mar 25, 2015 #2


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    I would say the first para is not at all a good answer. What is your source of information? The type of regulation in which the top operon is involved is called negative repressive regulation. You can read about it in easily browsed sources like https://www.boundless.com/biology/t.../the-trp-operon-a-repressor-operon-454-11679/ and also the.wikipedia article, but I would be surprised if you didn't have something similar from your course.

    As to the question what happens if the cell cannot produce tryptophan - it cannot grow or reproduce and eventually it will die. Unless you supply it with tryptophan in the medium and then it will grow and reproduce. In almost any experimental microbiology course you will soon come across nutritional or 'auxtrophic' mutants.

    Contrary to my initial impression from your first para the second showed you have grasped the princlple of repression. The kind of mutant that produces tryptophan even though supplied with it is called 'constitutive'. It grows OK but maybe slower than the the normal cell in the presence of the nutrient because it is wasting some resources synthesising unnecessary enzymes. Then there are factories using engineered overproducing strains to make the substance commercially.
  4. Mar 26, 2015 #3
    Hey thanks for your reply. The question actually asks if the mutation would inhibit the operon from committing its task, so i have to base my answer on that. That is why I believe it will be unable to metabolize it any longer, which it owuld appear that would lead to its death.

    I think i will do some research on this mutation as well. Thanks alot! (Unfortunately my teacher does not reply very often to her emails, so i cannot rely on her)
  5. Mar 26, 2015 #4


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    Question asked about mutation in operator region. Anyway in your reply you can state your understanding of what binds to what or doesn't and what effect that has on anything else.
  6. Mar 26, 2015 #5
    It seems I have a misunderstanding here. The TRP operon is what is used to signify the cell to produce tryptophan, and the repressor is what stops that from happening is what I believe to be the case. However, if the shape of the repressor is altered, then would this cause it to be unable to repress the production of tryptophan -> thus acting as if none were in the environment? Or would it be doing both at the same time?

    And I have asked my teacher about the question. She stated that the mutation is what is causing the operator to be unable to function. If this is the case, then it would not be able to produce tryptophan on its own, so if the environment had an absence of it, then it would lead to its death?

    Sorry for the questions. My course notes are really brief and they aren't providing me with leveled explanations.

    Just to add: If the operator is what causes the initation of the process(that is what i believe it to be?) and if there were no initiation to start the process then my guess is more or less on the right school of thought? From my current understanding(seems ot be very inaccurate though) the entire trp operon acts for the sake of producing tryptophan on its own. So it will be able to metabolize if the environment has enough to supply?
    Last edited: Mar 26, 2015
  7. Mar 26, 2015 #6


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    I have the impression you confuse the operon which is the whole thing with the operator (or operator sequence) which is one part.

    Inserted of relying on fragmentary notes you'd do better (learn how to learn) by using any textbooks available to you and the two links I directed you to to get the picture and terminology (and maybe make better notes of your own from them). An acquaintance with the examples of the gal operon and two or three others would be part of any general biological education I'd think.

    The question about changing the repressor shape is slightly vaguely expressed perhaps, but I suppose you know about specific recognition ability, which depends on the protein having a site of shape complementary to that of the molecule recognised. So by change shape they mean change, usually but not always decrease or lose, of this recognition ability. The repressor has to recognise two things, tryptophan and the operator sequence (and one recognition influences the other). So take it from there...
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